Control of load rejection

Abstract

A control system is provided for a power generating system having a gas turbine, a flue gas exhaust stage and a blow-off valve assembly. The gas turbine includes a compression stage, a combustion stage and a driveshaft. The blow-off valve assembly is configured to selectively provide fluid communication between the combustion stage and the flue gas exhaust stage. The control system includes a controller configured to output a signal causing the blow-off valve assembly to provide the fluid communication in response to a sudden de-loading of the gas turbine.

What is claimed is: 
     
       1. A control system for a power generating system having a gas turbine, a flue gas exhaust stage and a blow-off valve assembly, the gas turbine including a compression stage, a combustion stage and a driveshaft, the blow-off valve assembly being configured to selectively provide fluid communication between the compression stage and the flue gas exhaust stage by bypassing a combustion stage of the gas turbine, the control system comprising:
 a controller configured to output a signal causing the blow-off valve assembly to provide the fluid communication in response to a sudden de-loading of the gas turbine, 
 wherein the sudden de-loading is an at least 10 percent drop in mass flow through the compressor within a predetermined time period of less than 5 seconds. 
 
     
     
       2. The control system according to  claim 1 , wherein the sudden de-loading further includes an at least 10 percent or at least 15 percent drop in load applied to the driveshaft within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       3. The control system according to  claim 1 , wherein the sudden de-loading is an at least 15 percent drop in the mass flow through the compressor within a predetermined time period of less than 5 seconds, less than 2 seconds, or less than 1 second. 
     
     
       4. The control system according to  claim 1 , wherein the power generating system includes an electrical generator driven by the driveshaft, and the sudden de-loading further includes an at least 10 percent or at least 15 percent drop in electrical power output by the electrical generator within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       5. The control system of  claim 1 , wherein the gas turbine includes one or more sensors and the control system is configured to receive measurement values from one or more of the aforementioned sensor devices to ascertain whether sudden de-loading of the gas turbine has occurred. 
     
     
       6. A method of operating a power generating system having a gas turbine, a flue gas exhaust stage and a blow-off valve assembly, the gas turbine comprising a compression stage, a combustion stage and a driveshaft, the blow-off valve assembly being configured to selectively provide fluid communication between the compression stage and the flue gas exhaust stage by bypassing a combustion stage of the gas turbine, the method comprising:
 signalling the blow-off valve assembly to provide the fluid communication in response to a sudden de-loading of the gas turbine, 
 wherein the sudden de-loading is an at least 10 percent drop in mass flow through the compressor within a predetermined time period of less than 5 seconds. 
 
     
     
       7. The method according to  claim 6 , wherein the sudden de-loading further includes an at least 10 percent or at least 15 percent drop in load applied to the driveshaft within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       8. The method according to  claim 6 , wherein the sudden de-loading is an at least 15 percent drop in the mass flow through the compressor within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       9. The method according to  claim 6 , wherein the power generating system includes an electrical generator driven by the driveshaft, and the sudden de-loading further includes an at least 10 percent or at least 15 percent drop in electrical power output by the electrical generator within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       10. A method of modifying a power generating system having a gas turbine, a flue gas exhaust stage and a blow-off valve assembly, the gas turbine comprising a compression stage, a combustion stage and a driveshaft, the blow-off valve assembly being configured to selectively provide fluid communication between the compression stage and the flue gas exhaust stage by bypassing a combustion stage of the gas turbine, the method comprising:
 equipping the power generating system with a controller configured to output a signal causing the blow-off valve assembly to provide the fluid communication in response to a sudden de-loading of the gas turbine, 
 wherein the sudden de-loading is an at least 10 percent drop in mass flow through the compressor within a predetermined time period of less than 5 seconds. 
 
     
     
       11. The method according to  claim 10 , wherein the sudden de-loading further includes an at least 10 percent or at least 15 percent drop in load applied to the driveshaft within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       12. The method according to  claim 9 , wherein the sudden de-loading is an at least 15 percent drop in the mass flow through the compressor within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       13. The method according to  claim 9 , wherein the power generating system comprises an electrical generator driven by the driveshaft, and the sudden de-loading further includes an at least 10 percent or at least 15 percent drop in electrical power output by the electrical generator within a predetermined time period of less than 5 seconds, less than 2 seconds or less than 1 second. 
     
     
       14. A non-transitory computer-readable storage medium having stored thereon a computer program product that, when executed on a computer, causes the computer to output a signal causing a blow-off valve assembly to provide fluid communication between the compression stage of a gas turbine and a flue gas exhaust stage by bypassing a combustion stage of the gas turbine in response to a sudden de-loading of the gas turbine, wherein the sudden de-loading is an at least 10 percent drop in mass flow through the compressor within a predetermined time period of less than 5 seconds. 
     
     
       15. A power generating system comprising:
 a control system according to  claim 1 , a gas turbine, a flue gas exhaust stage and a blow-off valve assembly, the gas turbine having a compression stage, a combustion stage and a driveshaft, and the blow-off valve assembly being configured to selectively provide fluid communication between the compression stage and the flue gas exhaust stage by bypassing a combustion stage of the gas turbine. 
 
     
     
       16. The control system of  claim 15 , wherein the gas turbine includes one or more sensors and the control system is configured to receive measurement values from one or more of the aforementioned sensor devices to ascertain whether sudden de-loading of the gas turbine has occurred.